Electric valve

Abstract

To provide an electric valve which is easily worked and enables reduction of the cost thereof, and furthermore can secure a desired flow rate characteristics.SOLUTION: In an electric valve, a valve element portion of a valve stem includes a large diameter valve element cylindrical portion, a small diameter valve element cylindrical portion having a diameter smaller than that of the large diameter valve element cylindrical portion, and a small diameter tapered portion which is continuous with the small diameter valve element cylindrical portion. An orifice portion of the valve element includes a small diameter orifice cylindrical portion, and a large diameter orifice cylindrical portion having a diameter larger than that of the small diameter orifice cylindrical portion. When the valve stem is at a restriction position, the small diameter valve element cylindrical portion is positioned on a radial inward side of the small diameter orifice cylindrical portion, and the large diameter valve element cylindrical portion is positioned on a radial inward side of the large diameter orifice cylindrical portion. When the valve stem is displaced from the restriction position to an open position, the large diameter valve element cylindrical portion moves away from a radial inward side of the large diameter orifice cylindrical portion, and then the small diameter valve element cylindrical portion moves away from the radial inward side of the small diameter orifice cylindrical portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a motor-operated valve. [Background technology]

[0002] Conventionally, motor-operated valves have been used as devices that are placed in, for example, fluid piping paths to open and close the fluid flow path and control the flow rate. In such motor-operated valves, as shown in Patent Document 1, for example, a valve element is driven by a drive source such as a stepping motor attached to the valve body, ensuring accurate flow rate control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-180525 Summary of the Invention [Problem to be solved by the invention]

[0004] In motor-operated valves, it is sometimes desirable to control the opening of a valve so that a small amount of fluid can flow while maintaining a small opening immediately after the valve is opened. Even in this small opening state, it is necessary to suppress fluctuations in the flow rate of the fluid passing through the orifice.

[0005] To ensure stable flow control even at small openings, motor-operated valves have been developed in which the inner periphery of the orifice is elongated and cylindrical, and the outer periphery of the valve disc inside the orifice is elongated and cylindrical. With such motor-operated valves, the flow path cross-sectional area of ​​the gap formed between the orifice and the valve disc remains constant until the valve disc separates from the orifice when the valve disc is displaced axially relative to the orifice, thereby enabling stable flow control of the fluid flowing through the gap.

[0006] However, to achieve the above configuration, the inner periphery of the orifice and the outer periphery of the valve body facing it must be machined into a cylindrical shape with high precision over a certain distance, which requires a lot of machining work and increases the cost of the motor-operated valve.

[0007] An object of the present invention is to provide a motor-operated valve that can be easily manufactured and reduced in cost while still ensuring desired flow characteristics. [Means for solving the problem]

[0008] The motor-operated valve according to the present invention comprises: a valve body having a valve chamber and an orifice portion; a valve stem that is inserted through the orifice and has a valve body; a valve stem drive unit that can displace the valve stem relative to the valve body between a restricting position where the flow rate of fluid passing through the orifice portion is the smallest and an open position where the flow rate of fluid passing through the orifice portion is greater than that at the restricting position, the valve body portion has a large-diameter valve body cylindrical portion, a small-diameter valve body cylindrical portion having a diameter smaller than that of the large-diameter valve body cylindrical portion, and a small-diameter tapered portion continuing to the small-diameter valve body cylindrical portion, the orifice portion has a small-diameter orifice cylindrical portion and a large-diameter orifice cylindrical portion having a diameter larger than that of the small-diameter orifice cylindrical portion, When the valve stem is in the restricting position, the small-diameter valve body cylindrical portion is located radially inside the small-diameter orifice cylindrical portion, and the large-diameter valve body cylindrical portion is located radially inside the large-diameter orifice cylindrical portion, When the valve stem is displaced from the restricting position to the opening position, the large-diameter valve body cylindrical portion disengages from the radially inner side of the large-diameter orifice cylindrical portion, and then the small-diameter valve body cylindrical portion disengages from the radially inner side of the small-diameter orifice cylindrical portion. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a motor-operated valve that can be easily processed and reduced in cost, yet can ensure desired flow characteristics. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a motor-operated valve according to a first embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating the orifice portion and the valve body portion and their surroundings of the motor-operated valve of the first embodiment. [Figure 3] FIG. 3 is a flow rate characteristic diagram of the motor-operated valve of the first embodiment, with the vertical axis representing the flow rate and the horizontal axis representing the valve opening (axial position of the valve stem). [Figure 4] FIG. 4 is a cross-sectional view showing the periphery of a valve body portion and an orifice portion according to a comparative example shown in comparison with FIG. [Figure 5] FIG. 5 is a diagram schematically illustrating the orifice portion and the valve body portion and their surroundings of the motor-operated valve of the second embodiment. [Figure 6] FIG. 6 is a flow rate characteristic diagram of the motor-operated valve of the second embodiment, with the vertical axis representing the flow rate and the horizontal axis representing the valve opening (axial position of the valve stem). DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a motor-operated valve according to the present invention will be described with reference to the drawings.

[0012] [First embodiment] Fig. 1 is a longitudinal cross-sectional view showing the motor-operated valve 1 of the first embodiment. Fig. 2 is a diagram showing the orifice portion and the valve body portion of the motor-operated valve 1 in a simplified form, with some parts omitted. The axis of the motor-operated valve 1 is designated as L. In this specification, the direction from the rotor toward the valve seat is designated as downward, and the opposite direction is designated as upward.

[0013] 1, the motor-operated valve 1 includes a valve body 10, a guide bush 20, a valve stem holder 30, a valve stem 40, a can 55, a stepping motor 50 consisting of a rotor 51 and a stator 52, a compression coil spring (biasing member) 60, a locking member 70, a screw feed mechanism 28, and a lower stopper mechanism 29. In this embodiment, the stepping motor 50 and the screw feed mechanism 28 constitute a valve stem drive unit.

[0014] A flanged plate 18 is fixed to the upper end of the valve body 10 by brazing or the like. The lower end of a cylindrical can 55 with a ceiling abuts against a stepped portion provided on the outer periphery of the flanged plate 18 and is hermetically joined by welding.

[0015] A rotor 51 is rotatably disposed inside the can 55 and outside the guide bush 20 and the valve stem holder 30, and a stator 52 for driving the rotor 51 to rotate is disposed outside the can 55. The stator 52 is composed of a yoke 52a, a bobbin 52b, a stator coil 52c, and a resin molded cover 52d. A control signal including a drive pulse is input from the outside to the stator coil 52c via a substrate 52f to which lead wires 52g are connected, and excitation of the stator coil 52c causes the rotor 51 disposed inside the can 55 to rotate around the axis L at an angle corresponding to the drive pulse.

[0016] The rotor 51 disposed in the can 55 is fitted and supported by the valve stem holder 30, and the valve stem holder 30 rotates together with the rotor 51.

[0017] Specifically, the rotor 51 has a double-tube structure consisting of an inner tube 51a, an outer tube 51b, and a connecting portion 51c that connects the inner tube 51a and the outer tube 51b at a predetermined angular position around the axis L, and a plurality of vertical grooves 51d are formed on the inner circumference of the inner tube 51a, extending in the direction of the axis L (up and down) at angular intervals of, for example, 120 degrees around the axis L.

[0018] A plurality of ribs 30a extending in the vertical direction at intervals of, for example, 120 degrees around the axis L are protruded from the upper half of the outer periphery of the stem holder 30. On both sides of the lower part of the ribs 30a, upward-facing engagement surfaces (not shown) that support the rotor 51 are formed.

[0019] The longitudinal grooves 51d of the inner cylinder 51a of the rotor 51 engage with the ribs 30a of the stem holder 30, and the lower surface of the inner cylinder 51a of the rotor 51 abuts against the locking surface of the stem holder 30, so that the rotor 51 is supported and fixed in a state aligned with the stem holder 30. As a result, the stem holder 30 rotates together with the rotor 51 while supporting the rotor 51 within the can 55.

[0020] A cylindrical locking member 70 is provided above the rotor 51 and the stem holder 30 to prevent relative movement between the stem holder 30 and the rotor 51 in the vertical direction. The locking member 70 presses the rotor 51 downward against the stem holder 30 and connects the stem 40 and the stem holder 30.

[0021] The upper part of the locking member 70 is externally fitted and fixed to the upper end of the upper small-diameter portion 41 of the valve stem 40 by press-fitting, welding, or the like. A flange-shaped rotor retainer 72 is provided on the lower part of the locking member 70. The rotor 51 is sandwiched between the valve stem holder 30, which is urged upward by the urging force of the compression coil spring 60, and the rotor retainer 72. The vertical height from the upper end of the valve stem holder 30 to the locking surface is the same as the vertical height of the inner cylinder 51a of the rotor 51, and the upper surface of the top part 32 of the valve stem holder 30 abuts against the lower surface of the rotor retainer 72.

[0022] A return spring 75 made of a coil spring is fitted on the outer periphery of the locking member 70. If the stem holder 30 is displaced too far upward relative to the guide bush 20 when the valve is opened and the male thread portion 23 of the guide bush 20 and the female thread portion 33 of the stem holder 30 become disengaged, the return spring 75 biases the stem holder 30 toward the guide bush 20 to return these threads to their original state.

[0023] The valve stem 40, which is made of a metal material, has, from the upper side, an upper small diameter portion 41, an intermediate large diameter portion 42 having a diameter larger than that of the upper small diameter portion 41, and a valve body portion 43. The configuration of the valve body portion 43 will be described later.

[0024] The guide bush 20 has a thin-walled cylindrical portion 22, a thick-walled cylindrical portion 21, and a base portion 27 connected together. The thin-walled cylindrical portion 22 and the thick-walled cylindrical portion 21 have the same outer diameter, while the base portion 27 has a larger outer diameter. The thick-walled cylindrical portion 21 is fitted with the intermediate large-diameter portion 42 of the valve stem 40 so as to be relatively movable (slidable) in the direction of the axis L and relatively rotatable about the axis L. The thin-walled cylindrical portion 22, which extends upward from the upper end of the thick-walled cylindrical portion 21, has an inner diameter larger than that of the thick-walled cylindrical portion 21, and the upper end side of the intermediate large-diameter portion 42 and the lower end side of the upper small-diameter portion 41 of the valve stem 40 are inserted therein.

[0025] A male thread 23 is formed on the outer periphery of the thick-walled cylindrical portion 21 of the guide bush 20. A base 27, which is the portion of the thick-walled cylindrical portion 21 below the male thread 23, is press-fit into the fitting hole 14 of the valve body 10. A lower stopper 25 is fixed to the male thread 23 below the stem holder 30 by being screwed onto an upper surface 27a of the base 27 with a predetermined gap between them. A fixed stopper body 24 is integrally provided on the outer periphery of the lower stopper 25 so as to protrude.

[0026] The stem holder 30 has a cylindrical portion 31 into which the guide bush 20 is inserted, and a top portion 32. An insertion hole 32a is formed in the top portion 32, through which the upper end of the upper small-diameter portion 41 of the stem 40 is inserted. A female thread portion 33 is formed on the inner periphery of the cylindrical portion 31 of the stem holder 30. The female thread portion 33 is threadedly engaged with the male thread portion 23 of the guide bush 20 to form a screw feed mechanism 28. The screw feed mechanism 28 converts the rotational displacement of the rotor 51 relative to the valve body 10 into axial displacement of the valve stem 40.

[0027] A movable stopper body 34 is integrally provided to protrude from the lower end of the outer periphery of the cylindrical portion 31 of the stem holder 30. The fixed stopper body 24 and the movable stopper body 34 that constitute the lower stopper mechanism 29 engage with each other when the stem holder 30 has descended a predetermined amount, thereby restricting the downward rotation of the stem holder 30 and the stem 40 connected to the stem holder 30.

[0028] A compression coil spring (biasing member) 60 is compressed between an inner stepped surface formed between the upper small diameter portion 41 and the intermediate large diameter portion 42 of the valve stem 40 and the underside of the top portion 32 of the valve stem holder 30. The compression coil spring 60 constantly biases the valve stem 40 downward (in the valve closing direction) relative to the valve stem holder 30.

[0029] The valve body 10 is a cylindrical body made of metal such as brass or stainless steel. The valve body 10 has a valve chamber VC into which a fluid is introduced and discharged. A first conduit T1 is connected and fixed by brazing or the like to a first horizontal opening 10a provided on the inner periphery of the valve chamber VC. A partition wall 11 extending radially inward is formed at a middle position in the direction of the axis L of the valve body 10. A through-hole 11a is formed in the center of the partition wall 11, connecting the fitting hole 14 and the valve chamber VC. The intermediate large-diameter portion 42 of the valve stem 40 is slidably inserted through the through-hole 11a.

[0030] An orifice portion 13 is formed on the inside of the bottom wall 12 of the valve body 10, corresponding to the valve body portion 43 of the valve shaft 40, and a second conduit T2 is connected and fixed to an annular recess 10b formed on the underside of the bottom wall 12 by brazing or the like.

[0031] 3, the orifice portion 13 includes a first cylindrical orifice portion (small-diameter cylindrical orifice portion) 13a, a second cylindrical orifice portion (large-diameter cylindrical orifice portion) 13b formed above the first cylindrical orifice portion 13a and having a shorter axial length than the first cylindrical orifice portion 13a, an annular upper step portion 13f (not shown in FIG. 2) formed around the upper end of the second cylindrical orifice portion 13b, and an orifice taper portion 13c formed below the first cylindrical orifice portion 13a and increasing in diameter as it extends downward. A valve seat 13d is formed at the intersection of the first cylindrical orifice portion 13a and the upper step portion 13f. The first cylindrical orifice portion 13a is preferably machined using a drill or the like, while the larger-diameter second cylindrical orifice portion 13b and the like are preferably machined using a milling cutter or the like (i.e., in a separate process).

[0032] The valve body 43 includes a first valve body conical section (large-diameter tapered section) 43a formed at the lower end of the intermediate large-diameter section 42 and tapering downward; a first valve body cylindrical section (large-diameter valve body cylindrical section) 43b connected to the first valve body conical section 43a; a second valve body cylindrical section (small-diameter valve body cylindrical section) 43d connected to the first valve body cylindrical section 43b and longer in the axial direction than the first valve body cylindrical section 43b; and a third valve body conical section (small-diameter tapered section) 43e connected to the second valve body cylindrical section 43d. The third valve body conical section 43e may be a two-stage tapered section with different taper angles (shown as a single-stage tapered section in FIG. 2). The valve body 43 is preferably formed by lathe processing.

[0033] Here, if the outer diameter of the second valve body cylindrical portion 43d is B1 and the inner diameter of the first orifice cylindrical portion 13a is B2, the cross-sectional area Δ1 of the gap between the second valve body cylindrical portion 43d and the first orifice cylindrical portion 13a is Δ1=π((B2) 2 -(B1) 2 ) / 4.

[0034] Furthermore, if the outer diameter of the first valve body cylindrical portion 43b is B3 and the inner diameter of the second orifice cylindrical portion 13b is B4, the cross-sectional area Δ2 of the gap between the first valve body cylindrical portion 43b and the second orifice cylindrical portion 13b is Δ2=π((B4) 2 -(B3) 2 ) / 4, where Δ1<Δ2 is preferred.

[0035] Furthermore, when the valve is closed, it is preferable that A1≦A2, where A1 is the distance from the contact point between the valve seat 13d and the first valve body conical portion 43a to the lower end of the first valve body cylindrical portion 43b and A2 is the distance from the upper end of the second orifice cylindrical portion 13b to the lower end of the second valve body cylindrical portion 43d.

[0036] (Operation of the motor-operated valve) The operation of the motor-operated valve 1 will now be described. FIG. 3 is a flow rate characteristic diagram of the motor-operated valve 1, with the vertical axis representing flow rate and the horizontal axis representing valve opening (axial position of the valve stem), and schematically illustrates the positional relationship between the valve body portion 43 and the orifice portion 13. The valve opening is proportional to the drive pulse of the control signal applied to the stator coil 52c. In this embodiment, position P0 in FIG. 3 corresponds to the restricted position, and a position beyond position P0 in FIG. 3 corresponds to the open position. Also, just before the large-diameter valve body cylindrical portion separates from the radially inner side of the large-diameter orifice cylindrical portion, the lower end of the large-diameter valve body cylindrical portion is located radially inner side of the large-diameter orifice cylindrical portion. Also, just before the small-diameter valve body cylindrical portion separates from the small-diameter orifice cylindrical portion, the lower end of the small-diameter valve body cylindrical portion is located radially inner side of the small-diameter orifice cylindrical portion.

[0037] Assume that the motor-operated valve 1 is in the closed state shown in FIG. 1 , with the first valve-body conical portion 43a of the valve body 43 seated on the valve seat 13d (position P0 in FIG. 3 ). At this time, the second valve-body cylindrical portion 43d is located radially inside the first orifice cylindrical portion 13a (overlapping in the axial direction), and the first valve-body cylindrical portion 43b is located radially inside the second orifice cylindrical portion 13b (overlapping in the axial direction). From this state, a control signal including a drive pulse is supplied to excite the stator coil 52c of the stator 52, causing the rotor 51 to rotate in one direction, and the valve stem holder 30 and the valve stem 40 rotate integrally therewith. This rotation is converted into axial displacement of the valve stem 40 by the screw feed mechanism 28, causing the valve stem 40 to rise together with the valve body 43.

[0038] As the valve stem 40 rises, the second valve body cylindrical portion 43d is displaced axially relative to the first orifice cylindrical portion 13a, and the first valve body cylindrical portion 43b is displaced axially relative to the second orifice cylindrical portion 13b. As a result, the first valve body conical portion 43a and the valve seat 13d are separated from each other, creating a minimum gap exceeding zero. This allows a fluid such as a refrigerant to flow from the valve chest VC through the gap between the valve body portion 43 and the orifice portion 13 and into the second conduit T2. When the minimum gap between the first valve body conical portion 43a and the valve seat 13d is small (from position P0 to position P1 in Figure 3), the most constricted area between the valve body portion 43 and the orifice portion 13, i.e., the area with the smallest flow path step area (this is called the constricted area), is the area corresponding to the minimum gap between the first valve body conical portion 43a and the valve seat 13d, and therefore, as this minimum gap increases, the flow rate of the passing fluid increases linearly.

[0039] When the flow path cross-sectional area at the minimum gap between the first valve body conical portion 43a and the valve seat 13d exceeds the cross-sectional area Δ1 (position P1 in FIG. 3), the throttled region between the valve body portion 43 and the orifice portion 13 corresponds to the gap between the second valve body cylindrical portion 43d and the first orifice cylindrical portion 13a. Because the outer periphery of the second valve body cylindrical portion 43d and the inner periphery of the first orifice cylindrical portion 13a are both cylindrical, the cross-sectional area Δ1 in the throttled region does not change even if the valve shaft 40 is displaced. However, as the second valve body cylindrical portion 43d and the first orifice cylindrical portion 13a are displaced relative to each other in the direction of the axis L, and the first valve body cylindrical portion 43b and the second orifice cylindrical portion 13b are displaced relative to each other in the direction of the axis L, the overlapping range gradually narrows, thereby gradually reducing the pressure loss between the valve body portion 43 and the orifice portion 13, and the flow rate of the fluid passing through the throttling region gradually increases (the range from position P1 to position P2 in Figure 3).

[0040] 3, the first valve body cylindrical portion 43b is separated from the second orifice cylindrical portion 13b (the first valve body cylindrical portion 43b is no longer positioned radially inward of the second orifice cylindrical portion 13b), and therefore the gap between the first valve body cylindrical portion 43b and the second orifice cylindrical portion 13b is no longer involved in pressure loss. However, at this point, the second valve body cylindrical portion 43d is not separated from the first orifice cylindrical portion 13a (the second valve body cylindrical portion 43d is positioned radially inward of the first orifice cylindrical portion 13a), and therefore the throttle region is still the portion corresponding to the gap between the second valve body cylindrical portion 43d and the first orifice cylindrical portion 13a. Therefore, as the valve stem 40 rises, the second valve body cylindrical portion 43d and the first orifice cylindrical portion 13a are displaced relative to each other in the direction of the axis L, gradually narrowing the overlapping area, which further reduces the pressure loss between the valve body portion 43 and the orifice portion 13, and the flow rate of the fluid passing through the throttle region gradually increases (from position P2 to position P3 in Figure 3). Due to the difference in pressure loss in the orifice portion 13, the rate of increase in flow rate is higher from position P2 to position P3 in Figure 3 than from position P1 to position P2.

[0041] 3, the second valve body cylindrical portion 43d is separated from the first orifice cylindrical portion 13a (the second valve body cylindrical portion 43d is no longer positioned radially inside the first orifice cylindrical portion 13a), and hence the area corresponding to the gap between the third valve body conical portion 43e and the upper end of the first orifice cylindrical portion 13a becomes a throttle region, and as the valve stem 40 rises, the flow rate of the fluid passing between the valve body portion 43 and the orifice portion 13 increases linearly, making it possible to adjust the flow rate. Thereafter, the valve stem 40 rises to reach a fully open state (not shown).

[0042] On the other hand, when a control signal with reverse characteristics is supplied from the fully open state to excite the stator coil 52c of the stator 52 and rotate the rotor 51 in the reverse direction, the valve stem holder 30 and the valve stem 40 rotate together with the rotor 51. This is converted into axial displacement of the valve stem 40 by the screw feed mechanism 28, and the valve stem 40 moves down together with the valve body 43, resulting in the closed valve state shown in FIG. 1.

[0043] FIG. 4 is a cross-sectional view showing the periphery of the valve body portion 43' and the orifice portion 13' of the valve body 40' according to the comparative example. In FIG. 4, the valve body portion 43' has a first valve body conical portion 43a', a valve body cylindrical portion 43b', and a second valve body conical portion 43c'. The orifice portion 13' has an orifice cylindrical portion 13a' and a valve seat 13d'.

[0044] Further, when the outer diameter of the valve body cylindrical portion 43b' is B5 and the inner diameter of the orifice cylindrical portion 13a' is B6, the cross-sectional area Δ3 of the gap between the valve body cylindrical portion 43b' and the orifice cylindrical portion 13a' is Δ3 = π((B6) 2 -(B5) 2 ) / 4. Here, it is preferable that Δ2 > Δ1 > Δ3 holds.

[0045] Furthermore, when the valve is closed, the distance from the contact point between the valve seat 13d' and the first valve body conical portion 43a' to the lower end of the valve body cylindrical portion 43b' is defined as A3. It is preferable that A1 ≦ A2 < A3, and it is also preferable that A1 + A2 ≧ A3.

[0046] Here, since both the valve body cylindrical portion 43b' and the orifice cylindrical portion 13a' are formed by cutting, there are variations in the cross-sectional area Δ3 due to component tolerances. When it is desired to stably flow a small amount of fluid at a small opening while considering this variation, it is necessary to ensure a long distance A3. However, this increases the required number of drive pulses at the small opening, making it difficult to control the flow rate. Also, as the length of the drill for cutting the orifice cylindrical portion 13a' becomes longer relative to the diameter, the processing difficulty increases.

[0047] On the other hand, according to the present embodiment, since the orifice portion 13 has a first orifice cylindrical portion 13a and a second orifice cylindrical portion 13b, the length of the drill for cutting the first orifice cylindrical portion 13a can be shortened, making the processing easier and improving the yield. Also, the number of drive pulses from when the valve is closed until the first valve body cylindrical portion 43b detaches from the second orifice cylindrical portion 13b (position P2 in FIG. 3) can be reduced, making it easier to control the flow rate.

[0048] [Second embodiment] FIG. 5 is a longitudinal cross-sectional view showing a motor-operated valve 1A of a second embodiment. FIG. 6 is a flow rate characteristic diagram of the motor-operated valve 1A, with the vertical axis representing flow rate and the horizontal axis representing valve opening (axial position of the valve stem), and schematically shows the positional relationship between the valve body portion 43A and the orifice portion 13A. The motor-operated valve 1A of this embodiment is a so-called valve-closure-less type that does not completely close, and only the valve body portion 43A of the valve stem 40A and the orifice portion 13A of the valve body 10A differ from the first embodiment. Other configurations similar to those of the first embodiment are assigned the same reference numerals, and redundant explanations will be omitted. However, in this embodiment, positions P4 to P5 in FIG. 6 correspond to the restricted position, and a position beyond position P5 in FIG. 6 corresponds to the open position.

[0049] The orifice portion 13A has a first cylindrical orifice portion 13Aa, a second cylindrical orifice portion 13Ab formed in communication with the upper part of the first cylindrical orifice portion 13Aa and having a shorter axial length than the first cylindrical orifice portion 13Aa, an annular upper step portion 13Af formed around the upper end of the second cylindrical orifice portion 13Ab, and an orifice tapered portion 13Ac formed in communication with the lower part of the first cylindrical orifice portion 13Aa and having a diameter that increases downward. However, in this embodiment, the intersection of the first cylindrical orifice portion 13Aa and the upper step portion 13Af does not form a valve seat.

[0050] On the other hand, the valve body portion 43A has a first valve body cylindrical portion 43Ab connected to the lower end of the intermediate large diameter portion 42 of the valve stem 40A, a second valve body cylindrical portion 43Ad connected to the first valve body cylindrical portion 43Ab and longer in the axial direction than the first valve body cylindrical portion 43Ab, and a third valve body conical portion 43Ae connected to the second valve body cylindrical portion 43Ad. The third valve body conical portion 43Ae may be a two-stage tapered portion with different taper angles. However, there is no first valve body conical portion between the intermediate large diameter portion 42 and the first valve body cylindrical portion 43Ab, and the boundary between them is a step surface 43Af.

[0051] When the motor-operated valve 1A is in the minimum valve-open state shown in FIG. 5 (corresponding to positions P4-P5 in FIG. 6), the step surface 43f and the bottom wall 12A do not come into contact with each other, leaving a predetermined gap between them. At this time, the second valve body cylindrical portion 43Ad is located radially inside the first orifice cylindrical portion 13Aa, and the first valve body cylindrical portion 43Ab is located radially inside the second orifice cylindrical portion 13Ab. Therefore, the throttle portion between the valve body portion 43A and the orifice portion 13A corresponds to the gap between the second valve body cylindrical portion 43Ad and the first orifice cylindrical portion 13Aa. Therefore, even if the valve stem 40A rises from position P4 (minimum valve-open state) in FIG. 6 to position P5, where the pressure loss between the valve body portion 43A and the orifice portion 13A begins to decrease, no change in flow rate occurs. The subsequent process is the same as in the first embodiment.

[0052] When the valve shaft 40A rises further, as in the first embodiment, at position P6 shown in Figure 6, the first valve body cylindrical portion 43Ab separates from the second orifice cylindrical portion 13Ab (the first valve body cylindrical portion 43Ab is no longer positioned radially inside the second orifice cylindrical portion 13Ab), and at position P7 shown in Figure 6, the second valve body cylindrical portion 43Ad separates from the first orifice cylindrical portion 13Aa (the second valve body cylindrical portion 43Ad is no longer positioned radially inside the first orifice cylindrical portion 13Aa).Therefore, as the valve shaft 40A rises, the flow rate of the fluid passing through the valve body portion 43A and the orifice portion 13A increases, as in the first embodiment.

[0053] That is, when the valve shaft 40A is displaced from the restricting position to the opening position (from position P5 to position P7), the gap between the second valve body cylindrical portion 43Ad and the first orifice cylindrical portion 13Aa forms a throttling region until the second valve body cylindrical portion 43Ad separates from the radially inner side of the first orifice cylindrical portion 13Aa.

[0054] It should be noted that the present invention is not limited to the above-described embodiments. Any of the components of the above-described embodiments may be modified within the scope of the present invention. Furthermore, any of the components of the above-described embodiments may be added or omitted.

[0055] This specification includes the disclosure of the following inventions. (First aspect) a valve body having a valve chamber and an orifice portion; a valve stem that is inserted through the orifice and has a valve body; a valve stem drive unit that can displace the valve stem relative to the valve body between a restricting position where the flow rate of fluid passing through the orifice portion is the smallest and an open position where the flow rate of fluid passing through the orifice portion is greater than that at the restricting position, the valve body portion has a large-diameter valve body cylindrical portion, a small-diameter valve body cylindrical portion having a diameter smaller than that of the large-diameter valve body cylindrical portion, and a small-diameter tapered portion continuing to the small-diameter valve body cylindrical portion, the orifice portion has a small-diameter orifice cylindrical portion and a large-diameter orifice cylindrical portion having a diameter larger than that of the small-diameter orifice cylindrical portion, When the valve stem is in the restricting position, the small-diameter valve body cylindrical portion is located radially inside the small-diameter orifice cylindrical portion, and the large-diameter valve body cylindrical portion is located radially inside the large-diameter orifice cylindrical portion, When the valve stem is displaced from the restricting position to the opening position, the large-diameter valve body cylindrical portion disengages from the radially inner side of the large-diameter orifice cylindrical portion, and then the small-diameter valve body cylindrical portion disengages from the radially inner side of the small-diameter orifice cylindrical portion. A motor-operated valve characterized by:

[0056] (Second aspect) when the valve stem is displaced from the restricting position to the open position, the small-diameter valve body cylindrical portion separates from the radially inner side of the small-diameter orifice cylindrical portion, and then a gap between the end of the small-diameter orifice cylindrical portion and the small-diameter tapered portion forms a throttle region. The motor-operated valve according to the first aspect,

[0057] (Third aspect) the valve body portion has a large-diameter tapered portion, the orifice portion has a valve seat, and the large-diameter tapered portion is seated on the valve seat in the restricting position; The motor-operated valve according to the first or second aspect,

[0058] (Fourth aspect) when the valve stem is displaced from the restricting position to the opening position, after the flow path cross-sectional area between the small-diameter valve body cylindrical portion and the small-diameter orifice cylindrical portion exceeds the flow path cross-sectional area between the large-diameter tapered portion and the valve seat, a gap between the small-diameter valve body cylindrical portion and the small-diameter orifice cylindrical portion forms a throttle region. The motor-operated valve according to a third aspect,

[0059] (Fifth aspect) In the restricting position, the valve body portion does not contact the orifice portion. The motor-operated valve according to the first or second aspect,

[0060] (Sixth aspect) When the valve stem is displaced from the restricting position to the opening position, a gap between the small-diameter valve body cylindrical portion and the small-diameter orifice cylindrical portion forms a throttle region until the small-diameter valve body cylindrical portion separates from the radially inner side of the small-diameter orifice cylindrical portion. A motor-operated valve according to a fifth aspect, characterized in that: [Explanation of symbols]

[0061] 1. Motor-operated valve 10, 10A valve body 13, 13A Orifice part 20 Guide bush 23 Male thread 28 Screw feed mechanism 29 Lower stopper mechanism 33 Female thread 40, 40A valve stem 43, 43A Valve body 50 motor 51 Rotor 52 Stator VC valve chamber T1 1st conduit T2 2nd conduit

Claims

1. a valve body having a valve chamber and an orifice portion; a valve stem that is inserted through the orifice and has a valve body; a valve stem drive unit that can displace the valve stem relative to the valve body between a restricting position where the flow rate of fluid passing through the orifice portion is the smallest and an open position where the flow rate of fluid passing through the orifice portion is greater than that at the restricting position, the valve body portion has a large-diameter valve body cylindrical portion, a small-diameter valve body cylindrical portion having a diameter smaller than that of the large-diameter valve body cylindrical portion, and a small-diameter tapered portion continuing to the small-diameter valve body cylindrical portion, the orifice portion has a small-diameter orifice cylindrical portion and a large-diameter orifice cylindrical portion having a diameter larger than that of the small-diameter orifice cylindrical portion, When the valve stem is in the restricting position, the small-diameter valve body cylindrical portion is located radially inside the small-diameter orifice cylindrical portion, and the large-diameter valve body cylindrical portion is located radially inside the large-diameter orifice cylindrical portion, When the valve stem is displaced from the restricting position to the opening position, the large-diameter valve body cylindrical portion disengages from the radially inner side of the large-diameter orifice cylindrical portion, and then the small-diameter valve body cylindrical portion disengages from the radially inner side of the small-diameter orifice cylindrical portion. A motor-operated valve characterized by:

2. when the valve stem is displaced from the restricting position to the open position, the small-diameter valve body cylindrical portion separates from the radially inner side of the small-diameter orifice cylindrical portion, and then a gap between the end of the small-diameter orifice cylindrical portion and the small-diameter tapered portion forms a throttle region.

2. The motor-operated valve according to claim 1.

3. the valve body portion has a large-diameter tapered portion, the orifice portion has a valve seat, and the large-diameter tapered portion is seated on the valve seat in the restricting position; 3. The motor-operated valve according to claim 2.

4. when the valve stem is displaced from the restricting position to the opening position, after the flow path cross-sectional area between the small-diameter valve body cylindrical portion and the small-diameter orifice cylindrical portion exceeds the flow path cross-sectional area between the large-diameter tapered portion and the valve seat, a gap between the small-diameter valve body cylindrical portion and the small-diameter orifice cylindrical portion forms a throttle region.

4. The motor-operated valve according to claim 3.

5. In the restricting position, the valve body portion does not contact the orifice portion.

3. The motor-operated valve according to claim 2.

6. When the valve stem is displaced from the restricting position to the opening position, a gap between the small-diameter valve body cylindrical portion and the small-diameter orifice cylindrical portion forms a throttle region until the small-diameter valve body cylindrical portion separates from the radially inner side of the small-diameter orifice cylindrical portion.

6. The motor-operated valve according to claim 5.

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